Influences of joint immobilization and running exercise on articular cartilage surfaces of young rabbits. A semiquantitative stereomicroscopic and scanning electron microscopic study.

The influences of joint immobilization and running exercise on the articular cartilage surfaces of the patella and lateral tibial condyle of young rabbits were investigated by the semiquantitative stereomicroscopic and scanning electron microscopic methods during a period of 8 weeks. The smoothness of the articular surfaces was disturbed already 1 week after the onset of immobilization. Leafy, slightly rough and rough surface qualities associated with superficial splits were observed. The changes were of the same nature after a longer period of immobilization. Running exercise on the treadmill (150-300 m twice a day, 12-24 min per turn, 5 times a week) led to an increase of the striated surface quality at 1 to-2-week intervals as compared with the controls. It was apparent that during immobilization remarkable changes of the articular cartilage took place within the first week, while running exercise up to 8 weeks elicited only transient or minor alterations of the articular surface.